1. Field
The present invention relates to a bi-directional scan driver and a display device using the same.
2. Description of the Related Art
Recently, various flat panel displays that have reduced weight and volume in comparison to cathode ray tubes have been developed. As flat panel displays, there are liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), organic light emitting diode (OLED) displays, and the like.
Among the flat panel displays, the organic light emitting diode display, which displays images by using organic light emitting diodes (OLEDs) that generate light by recombining electrons and holes, has a fast response speed, is driven with low power consumption, and has excellent emission efficiency, luminance, and viewing angle, such that it has recently been in the spotlight.
Generally, the OLED display is classified as a passive matrix OLED (PMOLED) or an active matrix OLED (AMOLED) according to a driving method of the organic light emitting diodes (OLEDs).
The passive matrix OLED display uses a method in which an anode and a cathode are formed to cross each other and cathode lines and anode lines are selectively driven, and the active matrix OLED display uses a method in which a thin film transistor and a capacitor are integrated in each pixel and a voltage is maintained by a capacitor. The passive matrix OLED display has a simple structure and a low cost, however, it is difficult to realize a panel of a large size or high accuracy. In contrast, with the active matrix OLED display, it is possible to realize a panel of a large size or high accuracy, however it is technically difficult to realize the control method thereof and a comparatively high cost is required.
In view of resolution, contrast, and operation speed, the current trend is toward the organic light emitting diode (OLED) display of the active matrix type where respective unit pixels selectively turn on or off.
The organic light emitting diode (OLED) display of the active matrix type (e.g., AMOLED) includes a display device including pixels generally arranged in a matrix format, a data driver for transmitting data signals to data lines coupled to the pixels, and a scan driver for transmitting scan signals to scan lines coupled to the pixels.
In the driving method of the scan driver, the pixels are selected as a line unit (e.g., selected line by line) and the scan signal is sequentially supplied every horizontal period by using a plurality of shift registers included in the scan driver. The data driver supplies the data signals to the pixels selected as a line unit by the scan signal. Thus, the pixels display images corresponding to the data signals by supplying currents corresponding to the data signals to the respective organic light emitting diodes (OLEDs).
However, it is difficult for the above described one directional driving method in which the scan driver sequentially transmits the scan signal to the pixels to be applied to a portable communication device or a digital image device that has been developed recently according to various purposes and is equipped with various display panels that are changed according to an installation position when considering a viewing angle characteristic, such that driving of a bi-directional method has been proposed.
To drive the scan driver according to the bi-directional driving method regardless of the forward direction or the reverse direction, it is necessary to transmit the scan signal that is output from the scan driver to pixels of the display panel with a constant temporal sequence, and accordingly, a circuit design and development of such scan driver is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.